This invention relates to a system for flushing hydroformed parts to remove debris from inside the part.
In recent years, hydroforming technologies have become more and more important in manufacturing, particularly in the automotive industry. In one application of hydroforming, a tubular metal blank (usually steel) is placed in a die cavity. The opposite ends of the tube are sealed by a pair of hydraulic rams having central ports through which extremely high pressure fluid is injected into the tube. The high pressure fluid expands the tube into conformity with the surfaces defining the cavity. As a result of this hydroforming process, high strength parts can be made into complex tubular shapes that could otherwise not be achieved in any practical economic fashion. Such hydroforming processes are disclosed in U.S. Pat. Nos. 4,567,743; 5,070,717; 5,107,693; 5,233,854; 5,239,852; 5,333,755; and 5,339,667.
In even more advanced forms of hydroforming, the hydraulic rams are forced inwardly toward one another to create metal flow within the tube as the tube is being expanded in order to maintain the wall thickness of the tube within a predetermined range throughout the expansion process. Such hydroforming processes are disclosed in U.S. Pat. Nos. 5,718,048; 5,855,394; 5,899,498; 5,979,201; and 5,987,950.
For certain applications, it is desirable to produce a finished part that has a plurality of holes therein that can be used to mount other components. For example, in the automotive industry it is known to hydroform a tubular blank in order to form an engine cradle assembly used to mount an automotive engine. The finished tubular part must be provided with holes to enable fasteners to pass therethrough for mounting engine mounting brackets and the like. To facilitate the provision of holes in the part, it is known to perform a hole piercing operation in the hydroforming die itself. Typically, a hole is punched through the tube while under pressure. In one method, the portion of the tube cut out by the punch (sometimes referred to as the xe2x80x9cslugxe2x80x9d) has an edge portion thereof left connected to the tube, depending into the tube. This is problematic because it adds unnecessary weight to the part, which is always a concern in the automotive industry. In another method, after the hole is formed, the punch is withdrawn out of the tube, and formed by the punch is maintained in engagement with the punch under the force of fluid pressure as the punch is withdrawn from the tube. The slug is then flushed by fluid to a scrap collector. One such typical operation is disclosed by U.S. Pat. No. 5,816,089. One problem associated with the aforementioned technique is that on occasion the slug does not exactly align with the hole it came from as it is withdrawn and may fall into the tube. It must then be retrieved by other means.
It is an object of the present invention to a system for removing scrap from an interior of a hydroformed part.
Accordingly, the present invention provides a hydroforming assembly that has a plurality of die structures mounted on a press for reciprocating movement between open and closed conditions. The die structures have cooperating die surfaces defining a die cavity when in the closed condition and receive a metallic tube blank when in the open condition. A hydroforming fluid supply system has tube-end engaging structures that are movable to selectively and sealingly engage opposite ends of the tube blank. The hydroforming fluid supply system provides pressurized fluid into an interior of the tube blank in order to expand the tube blank outwardly into conformity with the die cavity. A punch extends within a passage of at least one of the die structures. The punch is movable between retracted and extended positions. A punch driving assembly drives the punch between the retracted and extended positions to punch a hole into the expanded tube blank. A flushing system communicates with the die cavity providing a flushing fluid flow through the interior of the tube blank.
According to another aspect of the invention, there is provided a method of forming a hole in a hydroformed metallic tube blank and removing a punched scrap therefrom. A plurality of die structures is provided on a press for reciprocating movement between open and closed conditions. The die structures have cooperating die surfaces defining a die cavity when in the closed condition. The die structures are provided in the open condition. A metallic tube blank is placed into the die cavity. The die structures are closed. An interior of the tube blank is pressurized with a fluid so as to expand the tube blank into conformity with the die cavity and thus form an expanded tube blank. A punch is forced through the expanded tube blank so as to punch a hole therein. The interior of the expanded tube blank is depressurized. Fluid is flowed through the expanded tube blank so as to flush a punched portion of expanded tube blank out from the interior thereof.